Outrage over families being separated at the U.S.-Mexico border has erupted as images of children being held in detention centers have been released.

Here’s everything you need to know about the zero-tolerance policy and how immigrant families are being impacted.

What is the new “zero tolerance” immigration policy?

The policy enforces that anyone caught crossing the U.S.-Mexico border illegally by Border Patrol, including those seeking asylum, will be prosecuted by the Department of Justice. If they have children with them, those children will be deemed “unaccompanied minors” and placed in detention centers.

In administrations past, families caught crossing the border illegally were prosecuted in only rare cases, according to Politifact. They were usually held in family detention centers until they were deported or sent to appear before an immigration court.

When and why was it created?

On April 6, Attorney General Jeff Sessions announced the “zero tolerance” policy for illegal entry on the Southwest border.

“The situation at our Southwest Border is unacceptable. Congress has failed to pass effective legislation that serves the national interest—that closes dangerous loopholes and fully funds a wall along our southern border. As a result, a crisis has erupted at our Southwest Border that necessitates an escalated effort to prosecute those who choose to illegally cross our border,” Sessions said.

In a May 7 speech, Sessions said while he understands that many of those crossing the border illegally are leaving difficult situations that the U.S. simply cannot take in “everyone on Earth in difficult situations” without hurting the interests and safety of U.S. citizens.

“If you are smuggling a child, then we will prosecute you and that child will be separated from you as required by law. If you make false statements to an immigration officer or file a fraudulent asylum claim, that’s a felony. If you help others to do so, that’s a felony, too. You’re going to jail. So if you’re going to come to this country, come here legally. Don’t come here illegally,” Sessions said.

CNN acquired documents showing that the Trump administration presumed the new policy would deter immigrant families from trying to enter the country.

“The full impact of policy initiatives are not fully realized for 2-3 weeks following public messaging — however, some migrants already underway may temporarily halt to determine the effects of the new policy,” the document states.

Is it really “the law” to separate immigrant families at the border?

President Trump and members of his administration have claimed they are adhering to the law by separating immigrant families on the U.S.-Mexico Border, with the President going on Twitter to blame Democrats and calling on them to “end the horrible law that separates children from there (sic) parents once they cross the Border into the U.S.”

But no law exists saying children must be separated from their parents if they cross the border illegally.

The Department of Homeland Security told Politifact that there is a longstanding policy that children of parents charged with a federal misdemeanor are transferred into the custody of the Health and Human Services’ Office of Refugee Resettlement and are then either placed with their relatives, foster care, or a juvenile detention center.

The reason immigrant families are now being separated is that the current administration is prosecuting all those crossing the border illegally, including those who may be seeking asylum. When parents are prosecuted their children are separated from them and placed in detention centers.

Where are they being placed?

In detention facilities by the Department of Homeland Security and the Office of Refugee Resettlement, a division of Health and Human Services. Reporters, lawmakers, and activists have visited these centers and their first-person accounts have garnered global attention.

JUST IN: Video from inside our tour of the Border Patrol's processing station in McAllen — the epicenter of family separations.

You'll see single adult males, but at about 53 seconds in it gets to mothers and girls.

"People in here are locked up in cages, essentially what look like animal kennels. I don't know any other way to describe it"@jacobsoboroff reporting from the border detention centers pic.twitter.com/gnwFiFFmze

One detention center in McAllen, Texas is referred to as “the dog kennel” for its metal fencing and cages.

“More than 1,100 people were inside the large, dark facility that was divided into separate wings for unaccompanied children, adults on their own and mothers and fathers with children,” AP reports. “The cages in each wing open into common areas, to use portable restrooms. The overhead lighting stays on around the clock.”

About 200 people inside were minors unaccompanied by a parent, while another 500 were family units of parents and children.

The latest reports from the border indicate that large groups of children are being held in cages and some children are so traumatized they've attempted suicide. President Trump could end this horrific policy TODAY. If he won't, Congress must pass the #KeepFamiliesTogetherAct

"A toddler inside the 60-bed facility caught her eye — she was crying uncontrollably and pounding her little fists on mat…She had been taken from her mother the night before and brought to the shelter." https://t.co/bOYQLmVioB

How many children have been separated from their families?

A Reuters report published on June 8 says nearly 1,800 families have been separated by border agents between October 2016 and February 2018.

“If that’s indeed the case, the Trump administration would have installed this type of policy earlier than previously thought,” PBS reports. “The exact origins on when the Trump administration rolled out this policy have not been cleared up by federal officials.”

On June 15, DHS confirmed that 1,995 children were separated from 1,940 adults at the U.S.-Mexico border from April 19 through May 31.

Do they have any contact with their parents or family members?

The policy to prosecute anyone found crossing the border illegally has inevitably caused work to pile up for defense attorneys and has made it difficult for families to reunite.

Often, mass hearings take place for families looking for their children, with as many as 75 defendants in one hearing. In one such hearing in McAllen, a mother was told by an immigration judge, “I have no information about your child,” Vice reported.

However, under the policy, the DHS says parents and children will be reunited after the parents’ criminal case is completed and they are returned to Immigration and Customs Enforcement. But Vox says, “It’s not clear how ICE is going to guarantee reunification. Some parents have ended up separated from their children for months, even after being released from immigration detention.”

According to the DHS website, “ICE will work with detained parents to provide regular communication with their children through video teleconferencing, phone, and tablets.”

How long is the average child in a detention center?

While the children are in HHS care, the ORR begins looking for a sponsor for the child so they can be discharged from federal custody. The DHS says, A sponsor can be a parent, adult sibling, relative, or appropriate home that meets criteria for the safety of the child and continuation of any immigration proceedings. A parent who is prosecuted and later released can be a sponsor and ask HHS to release his or her child back into his or her custody.

The website does not explicitly state the average amount of time children are in their care, but the Flores Settlement, a court order established in 1997, mandates that immigrant children in custody be placed with a close relative “without unnecessary delay” to ensure children aren’t held indefinitely.

How have Democrats reacted to the policy?

Democratic lawmakers, along with activists and reporters, have visited detention centers in Texas and New Jersey to further look into the conditions children there are subjected to.

Those who visited the Customs and Border Protection processing detention center in McAllen, Texas say they were dismayed by what they saw.

“We did see the children who were held inside here,” Oregon Democratic Senator Jeff Merkley told CNN. “In wire-mesh, chain linked cages that are about 30×30, a lot of young folks put into them. I must say though, far fewer than I was here two weeks ago. I was told that buses full (of children) were taken away before I arrived. That was one of my concerns, that essentially, when you have to give lengthy notice, you end up a little bit of a show rather than seeing what’s really going on in these centers.”

Former President Bill Clinton took to Twitter to denounce Trump’s alleged use of the children as a “negotiating tool” to get Democrats to accept immigration limits.

On this Father’s Day I’m thinking of the thousands of children separated from their parents at the border. These children should not be a negotiating tool. And reuniting them with their families would reaffirm America’s belief in & support for all parents who love their children.

How have Republicans reacted?

“The reason for these separations is a zero-tolerance policy for their parents, who are accused of illegally crossing our borders,” Bush wrote. “I appreciate the need to enforce and protect our international boundaries, but this zero tolerance policy is cruel. It is immoral. And it breaks my heart.”

First Lady Melania Trump even voiced her disapproval of the separations but hopes “both sides of the aisle can finally come together to achieve successful immigration reform.”

Republican Senator Susan Collins, from Maine, appeared on “Face the Nation” on CBS to speak out about the policy this past Sunday.

“What the administration has decided to do is to separate children from their parents to try to send a message that, if you cross the border with children, your children are going to be ripped away from you,” she said. “That is traumatizing to the children, who are innocent victims. And it is contrary to our values in this country.”

Few have to come out to openly support the separations, with the White House trying to distance itself from it. In a series of tweets released on Sunday, Secretary of Homeland Security Kirstjen Nielsen wrote: “We do not have a policy of separating families at the border. Period.”

While there have been reports of asylum seekers arriving at ports of entry and being placed into custody according to the New York Times, Nielsen says, “For those seeking asylum at ports of entry, we have continued the policy from previous Administrations and will only separate if the child is in danger, there is no custodial relationship between ‘family’ members, or if the adult has broken a law.”

Former White House Chief Strategist Steve Bannon said there’s no need for President Trump to justify the policy.

“It’s a crime to come across illegally, and children get separated,” he told ABC. “I mean, I hate to say it, that’s the law and he’s enforcing the law.”

The public backlash has led Sessions to address the criticism as he received a lifetime achievement award from the National Sheriffs Association on Monday.

“We do not want to separate children from their parents but we do not want adults to bring children into this country unlawfully either, placing those children at risk,” Sessions said. “But we do have a policy of prosecuting adults who come here illegally instead of waiting their turn or claiming asylum in any of our ports of entry. They can go to our ports of entry if they want to claim asylum and they won’t be arrested. We cannot and will not encourage people to bring their children to the country unlawfully by giving them immunity in the process.”

Children are being used by some of the worst criminals on earth as a means to enter our country. Has anyone been looking at the Crime taking place south of the border. It is historic, with some countries the most dangerous places in the world. Not going to happen in the U.S.

How does Congress plan to address the policy?

The President has made clear that the family separation debate has been used to leverage for a “broader immigration overhaul,” but CNN says, “there is no bipartisan immigration overhaul in the works in either chamber.”

California Democratic Senator Dianne Feinstein introduced a law that would directly address the issue, and all the senators who caucus with Democrats have signed on to co-sponsor the legislation. Feinstein has urged citizens to call their Republican senators in an effort to get to them to join.

UPDATE: The entire Democratic caucus supports our bill to bar children from being taken from their parents at the border. I’ve heard countless Republicans say that they oppose children being taken from their parents. If that’s true, they should support our bill NOW!

Utah Republican Senator Orrin Hatch said in a statement that he would be “working with colleagues in both chambers on a path forward that recognizes the need for compassion for children and families without incentivizing illegal border crossings. That solution can and should be bipartisan.”